While the drilling of holes in a wall structure, e.g. of masonry or plastic, is not particularly difficult utilizing a conventional drill bit and where necessary, the various commercially available guides or the like for ensuring that the drill bit will not move excessively from the site of the hole, there are, however, cases in which the drilling of such holes poses a significant problem. One such case is where the drilling must be effected through a wall covering having a fabric or fibrous construction and or a bulky or pad construction.
Such wall coverings are utilized from time to time for esthetic, sound-damping and artistic effects and include fabric wall coverings, fabrics applied to fabric backings, wall coverings with fabric backings and various blanket and carpeting fabrics which may be cemented or otherwise bonded to foam or other materials. Duffle, flannels and like materials have been utilized or proposed as either the outer or the backing layers in such comparatively thick wall coverings.
When attempts are made to drill into the underlying wall through such materials utilizing conventional drill bits with or without guides of the type hitherto provided, problems are encountered not only because there is a tendency to damage the outer fabric but also because of the tendency for the fibers of the underlying layer to entwine around a bit and to be pulled from the fabric and/or a support or cushion. This can cause degradation of the wall covering over substantial areas and damage which encompasses regions far larger than the particular hole.
The problem can be overcome in part by cutting the wall covering as part of the drilling process or prior to the drilling process utilizing special cutting tools which can be provided for this purpose. Not only is such a cutting operation difficult to carry out but it is not always successful since if even a single fiber from a funnellike backing layer remains to entwine around the drill, serious degradation can occur. An alternative approach, of course, is to cut through the fabric and its backing with a much larger diameter than the hole which is to be ultimately drilled, e.g. to form a passage about three times larger than the hole to ensure that there will be no residual fibers or threads which can be pulled by the drill. This, of course, damages the esthetic effect because, even if a small hole is to be made, a larger piece of wall covering which may have to be cut out generally will render the operation unsightly.